Intraoperative ventricular mapping is the technique of recording cardiac electrical activity directly from the heart. The recording sites are usually identified from an anatomical grid and may consist of epicardial, intramural, and endocardial sites. A probe with electrodes is used to explore these surfaces and generate a map that displays the sequence of electrical activation. This information is used by the surgeon to locate precisely the site of an operative intervention.

The intraoperative ventricular mapping procedure is covered under Medicare only for the uses and medical conditions described below:

• Localize accessory pathways associated with the Wolff-Parkinson-White (WPW) and other preexcitation syndromes;
• Map the sequence of atrial and ventricular activation for drug-resistant supraventricular tachycardias;
• Delineate the anatomical course of His bundle and/or bundle branches during corrective cardiac surgery for congenital heart diseases; and
• Direct the surgical treatment of patients with refractory ventricular tachyarrhythmias.